1. Field of the Invention
The present invention relates to a magnetic recording medium and an apparatus and a method for reading data from the magnetic recording medium, and more particularly, to a magnetic recording medium and an apparatus and a method for reading data from the magnetic recording medium using spin-dependent scattering of electrons.
2. Description of the Related Art
In general, there are two conventional methods for reading data recorded on a magnetic recording medium. One involves detecting a magnetic field generated from the magnetic recording medium, and the other involves taking advantage of a magneto-optical effect. However, as the density of data recorded on data storage media increases and the size of a bit, the smallest unit of data recorded on the data storage medium, decreases, these two methods become more susceptible to technical problems. For example, in the case of the method of reading data from a magnetic recording medium by detecting a magnetic field generated from the magnetic recording medium, despite aggressive research on reducing the size of a bit, there is still a limit to the size of a magnetic field sensor. In addition, decrease in the size of a bit is accompanied by decrease in the intensity of output signals, and current technology is incapable of amplifying output signals beyond a certain level. In the case of the method of reading data from a magnetic recording medium taking advantage of a magneto-optical effect, the fact that resolution is determined by the wavelength of light used imposes restrictions on recording density that can be applied to a magnetic recording medium.
In order to solve the technical problems of the conventional data reproduction methods, U.S. Pat. No. 6,304,481 discloses an apparatus and a method for storing data using spin-polarized electrons.
FIG. 1 is a cross-sectional view of a data storage device taught by the U.S. Pat. No. 6,304,481 patent. Referring to FIG. 1, the data storage device includes a control unit 1, a spin-polarized electron source 40 having a tip 2b, an extractor 4, collimators 6, 7, and 9, electrostatic lenses 10, 11, and 12, and insulating elements 5 and 8. The data storage device also includes a blanking element 13, coarse and fine microdeflectors 14 and 15, respectively, an electron detector 16, a data storage layer 17, and a substrate 18.
The control unit 1 receives control signals and data from an external device via ports ADDRESS IN, DATA IN, and DATA OUT, interprets the control signals and the data using necessary protocols, and returns control responses and data to the external device.
The electron source 40 provides spin-polarized electrons 3, and then tip 2b collects the spin-polarized electrons 3. The extractor 4 extracts the spin-polarized electrons 3 from the tip 2b, and the collimators 6, 7, and 9 collimate the spin-polarized electrons 3 into a spin-polarized electron beam 19. The electrostatic lenses 10, 11, and 12 focus the spin-polarized electron beam 19, and the microdeflectors 14 and 15 deflect the spin-polarized electron beam 19 toward a magnetic field generated in part of the data storage layer 17 on which data will be stored.
The data storage layer 17 includes a plurality of alignment regions 22 and a conductive element 27 insulated from the data storage layer 17 by the insulating element 28.
The control unit 1 applies a voltage V1 to the electron source 40 and voltages V2 through V5 to the extractor 4 and the collimators 6, 7, and 9, respectively, in order to obtain desired characteristics of the spin-polarized electron beam 19. Voltages V6 through V8 are applied to the electrostatic lenses 10, 11, and 12, respectively, by the control unit 1 to create electrostatic fields through lens apertures. Voltages V12 through V19 are applied to an end of a stigmator 25 by the control unit 1. The control unit 1 applies a signal S19 to the spin-polarized electron source 40 to determine a direction of polarization of the spin-polarized electrons 3 and applies signals S2 through S17 to the coarse and fine microdeflectors 14 and 15, respectively, to deflect the spin-polarized electron beam 19. In addition, the control unit 1 applies a signal S1 to the blanking element 13 and reads data by alternately detecting signals S18 and S20.
According to the data storage device and method disclosed in the U.S. Pat. No. 6,304,481 patent, it is necessary but not at all easy to minutely control voltage in order to concentrate the electron beam on a specific data storage region. In addition, in order to inject the electron beam onto the data storage medium, there must be a non-conductive space provided on the data storage medium, which results in lower efficiency and makes it harder to precisely output detection signals used to reproduce data from the data storage medium.